There is a need to store information for long periods of time without the use of power. For example, in many electronic devices and systems, data can be stored in a nonvolatile memory, or quasi-nonvolatile memory. A quasi-nonvolatile memory can be a memory with a ‘refresh’ interval orders of magnitude longer than a dynamic random access memory (DRAM).
One type of memory is a conductive bridging random access memory (CBRAM). A CBRAM can have memory elements that store information in terms of the resistance level of two-terminal structure. Changes in resistance can come about by a reduction-oxidation reaction of one or more memory layers caused by the application of bias voltages.
Conventionally, nonvolatile memory cells utilize access devices formed in a substrate. For example, “flash” electrically erasable and programmable read only memory (EEPROM) cells can include one or more transistors formed in a substrate that store data by the presence of charge on a floating gate. Thus, substrate area must be dedicated to such memory cells. Flash EEPROMs can also require specialized fabrication processes. While conventional CBRAM based memories can form storage elements over a substrate, such elements are accessed by access devices formed in a substrate (e.g., silicon based transistors, diodes, thyristors, etc.).